When position references such as “above”, “in front” or the like are mentioned in this document, the weapon is assumed to be in normal firing position, firing horizontally “forward” (i.e., away from the shooter).
U.S. Pat. No. 4,133,128, DE-OS 1 428 772 and EP 0 204 691 A2 are known prior art.
Automatic weapons, such as machine guns or sub-machine guns, which are only intended for sustained fire have a rather simple trigger mechanism. As used herein, the term “automatic firearm” is intended to encompass all rapid-firing weapons including machine guns and sub-machine guns. A representative example of a prior art trigger mechanism for an automatic firearm is described in the following.
Beneath the motion path of the breech there is a butt, in which a trigger is swivel-mounted. The swivel axis, which proceeds laterally to the longitudinal axis of the firearm, is located over the trigger, so that, upon operation of the trigger, the rear upper part travels a curved path upward. This rear upper part of the trigger acts on the front end of a breech catch. The breech catch is mounted in the weapon casing or in the butt and can be pivoted around an axis which is also lateral to the longitudinal axis of the firearm. The rear end of the breech catch is constructed as a sear arm. When the trigger is pressed forward to its resting position by a trigger spring, then the front end of the breech catch moves downward, and the sear arm moves upward. This upper position of the sear arm is the locking position.
The breech catch is usually cushioned by a separate spring, which forces it into the locking position. If the breech is pulled back to its resting position with the breech catch in its locking position, then the breech moves the sear arm and, thus, the rear end of the breech catch downward as it passes at least partially over the sear arm. When a sear catch, which is constructed on the bottom of the breech, has passed over the sear arm, then the sear arm snaps upward and engages the sear catch to hold the breech in its rearward position. The weapon is now cocked and ready to fire.
When the trigger is operated, then the sear arm sinks until it releases the sear catch and the weapon begins sustained fire. When the trigger is released, then the sear arm and the sear catch move up to hold the breech in its fire readiness position (rear position). As a result, the sustained fire ceases.
Usually only a safety catch is used as a safety mechanism. While the safety catch rules out unintentional operation of the trigger, it does not rule out a giving way of the sear arm due to, for example, forces of gravity, if the loaded, cocked and trigger-secured machine gun falls off a truck.
While one could also lock the breech catch for security, such an approach has the disadvantage that the breech gets jammed over the breech catch when it is pulled back with a locked weapon, because the breech catch cannot give way.
It is proper to put the weapon on safety when an extraordinary situation occurs. An empty magazine or the end of the ammunition belt can be an extraordinary situation for inexperienced shooters if the breech is located in the front position. However, particularly in the case of a jammed loading mechanism, the attention of the shooter may be completely occupied, so that a mistaken operation of operating devices can occur. In the case of a jammed loading mechanism, the breech should, as the first measure, be pulled back so far that the sear arm falls into the sear catch, so that the caught breech does not come loose, run to the front and inadvertently trigger a shot.
At least in training and at the shooting range, it is also desirable that the breech be pulled back when the safety is on and the firearm not be ready to fire until right before the shot is fired. However, up to now this has only been possible with safety catches.
Only in FIG. 1 are all of the drawing reference numerals entered. For reasons of clarity, certain reference numerals have been omitted in FIGS. 2 through 5. However, all of the figures show the same weapon. Therefore, the drawing reference numerals as used in FIG. 1 are valid for all of the figures.